Das Geld mit steigt - davon bemerke ich nichts - jedenfalls nicht bei den Mediums und auch nicht bei den TDs. Das einzige was steigt sind die Rep-Kosten und die Preise für die Munition.
Die credits die man verdient steigen automatisch mit höheren Stufen:
http://wiki.worldoftanks.com/Battle_Mechanics#Earning_CreditsEarning Credits
Credits are awarded for participating in battle and battle performance (mostly for damage inflicted in HP).
Payment for battle participation
Payment for battle - guaranteed amount of credits, independent of the tank's performance in battle - is proportional to the tank's tier (essentially it's worth in battle).
Payment for battle consists of: X * tank-tier for defeat or a tie, and 1.85X * tank-tier for victory.
Payment for inflicting damage to the enemy
For every point of damage inflicted, the tank receives Y credits, independent of the tier. You will get 0.1Y bonus credits per tier difference of the enemy tank, in comparison to yours (enemy tank tier - yours = 0.1Y per tier difference) Damage inflicted by fire is counted towards the player who set the fire. In case of ammo rack explosion or other damage by initial fire, all damage is counted towards the player who set it.
Damage is counted if inflicted on the enemy. Damage by friendly fire is not counted. Unintentional kills (frag) are not individually counted towards the payment.
If shooting a target spotted by another then you receive 0.5Y credits for damage. If the enemy is damaged by another teammate when spotted by the player, then the player receives up to 0.5Y credits for damage.
Payment for spotting
For all initial spotting of enemy tanks, the player receives Z credits, and 2 * Z for damaging SPGs.
Payment for base capture
Base capture is paid out with a certain sum of credits. Payment is independent of the number of tanks and their tiers - everyone in the circle receives the payment equally. This only applies to sucessful captures. Interrupted captures will not earn you anything.
Balance coefficient
It is a factor for individual setting of tank profitability. Payment for all vehicles, except premium, is multiplied by the coefficient W. The given coefficient for premium vehicles is higher.
The average tank has an average coefficient of 0.65 - 0.71, except for premium tanks, which have 1.10-1.3 (Information to be updated as for April 11th, 2011).
Premium Account
For premium accounts, credits are multiplied by 1.5
Not Paid
Complete destruction of the enemy team is NOT specifically awarded. It is way more valuable FOR YOU to capture the enemy base rather than killing them all.
Of course if YOU are not in the enemy capture zone, you will not share in the rewards.